NEOWISE, the Near-Earth Object Wide-field Infrared Survey Explorer, is a space telescope that detects, tracks and characterizes moving solar system objects, including near-Earth asteroids. It surveys the sky in infrared, which makes it particularly well-suited to observing very dark asteroids that do not reflect much visible light.
Originally launched as WISE in 2009, the telescope and its 4 infrared detectors were kept chilled inside a tank with frozen hydrogen-filled walls to prevent WISE from detecting its own heat. It scanned the sky for the nearest and coolest stars, the most luminous galaxies in the universe, and asteroids.
The spacecraft's hydrogen supply ran out as expected in 2010, rendering 2 of its detectors useless. After a 30-month hibernation, NASA reactivated the spacecraft as NEOWISE in 2013. The mission implemented a new data processing pipeline that was designed to work best on solar system objects that have detectable motion. NEOWISE is expected to operate until atmospheric drag shifts its orbit to the point where it will be unable to make observations without sunlight or reflected Earth light entering the telescope. The estimated soonest that would happen is June 2019.
To find the most luminous galaxies in the universe
To find and study asteroids in our solar system
To better understand the evolution of planets, stars and galaxies
During its primary mission, WISE scanned the entire sky twice in infrared, snapping pictures of three-quarters of a billion objects. By February 2011, at the end of the primary mission and 4-month NEOWISE Post-Cryogenic Mission, the space telescope had detected more than 157,000 moving solar system objects that included at least 584 near-Earth objects, roughly 2,000 Jupiter Trojans, 18 Centaurs and scattered-disk objects, and about 120 comets. WISE also detected a handful of irregular satellites of Jupiter and Saturn, including Iapetus and Phoebe, as well as cometary dust trails and dust bands in the zodiacal cloud.
This top-down view of the solar system shows the positions on 15 December 2018 of all main belt asteroids (grey circles), near-Earth asteroids (green circles) and comets (yellow squares) detected by NEOWISE during its first 5 years of operations since reactivation.White circles show objects detected during the final week of year 5. The blue circles and points indicate the orbits and locations of Mercury, Venus and Mars. The Earth and its orbit are shown in cyan.
The overall goal of NEOWISE is to detect, track and characterize near-Earth asteroids. The goal of the 3-year primary mission, which started in December 2013, was to observe the entire sky 6 times using the telescope's remaining 2 infrared detectors.
Dimensions: 2.85 meters along telescope axis, 2 meters wide on solar panel axis, 1.7 meters deep.
Power: NEOWISE's fixed solar arrays can provide up to 551 watts of power; on average the spacecraft consumes 301 watts.
Cooling: WISE's cyrostat cooling system, which surrounds the telescope and its infrared detectors, used a primary and secondary frozen hydrogen tank to chill the telescope's two longer-wavelength detectors to less than 8 Kelvin. The hydrogen supply was expected to last 10 months, and lasted until roughly 10-and-a-half months after launch.
Orbit: WISE was launched into a 525-kilometer, circular, sun-synchronous polar orbit with an inclination of 97.5 degrees. Over time, atmospheric drag has caused it to drift into what is now a 481 x 487-kilometer orbit with an inclination of 97.4 degrees.
The orbit allows the spacecraft to stay in sunlight continuously, with its solar arrays face-on to the Sun while the telescope points perpendicular into space. As the spacecraft continues to drift, it will eventually be unable to observe without sunlight or reflected Earth light entering the telescope, which will end the mission.
Launch vehicle: Delta II 7320-10 from Vandenberg Air Force Base
WISE telescope design
A labeled schematic of the WISE / NEOWISE telescope's major components.
NEOWISE is equipped with a 40-centimeter-diameter telescope. Light from the telescope is routed to 4, 1-megapixel infrared detectors tuned to distinct wavelengths: 3.4, 4.6, 12, and 22 μm (designated W1, W2, W3, W4, respectively). After the telescope's frozen hydrogen supply ran out, only the shorter-wavelength 3.4 and 4.6 μm detectors remained usable.
WISE’s 1-million-pixel detectors were a vast improvement over the 1983 Infrared Astronomical Satellite’s 62-pixel detectors. The James Webb Space Telescope will improve on WISE with 4-million-pixel detectors in the 0.6 to 5 μm range, and 1-million pixel-detectors up to 28 μm.